Most commercially available software products undergo a continual revision process to repair or upgrade features and/or functions. Each revision of a software product or component may require the addition of new files and/or the replacement of existing files with files of newer versions. Once a vendor has isolated a software product problem and created a solution for the problem, it would want to put that fix into an update and make the update widely available to the customers. Software vendors have a business incentive to distribute software updates to customers as quickly and trouble-free as possible.
The Internet provides an important channel for customers to obtain the latest updates for software products. The explosive growth of Internet usage has created a common expectation by customers that software products and updates be provided online for downloading. It is also in the interest of software vendors to promote the use of the Internet to distribute updates, because it reduces their costs and allows customers to obtain the fix for an identified problem as soon as the fix is made available for downloading. The vendor sites on the Internet can be designed to make it very simple to discover and locate update files for an application. The technical aspects of file download have mostly disappeared from the user's view, and are now typically handled by the operating system.
In a conventional approach, a software vendor constructs a software update as a “package” for download. This package is typically a self-extracting executable file with the setup program and each of the product's updated files embedded and compressed to make the package smaller. The size of the package is generally the sum of the compressed sizes of each changed file, plus the size of the extraction code itself. Upon execution, the package extracts each of the contained files to a temporary location, then starts the setup program to install each file to a proper location in the system's directory. Files that are shipped in a compressed form are decompressed as they are installed. Any existing file of the same name in the same location would simply be overwritten by the replacement file.
Even though the Internet makes wide and quick distribution of software updates possible, the limited bandwidth of network transmission has caused problems. The sheer sizes of common software applications have caused the download sizes of updates to become unreasonably large. Usually a multitude of fixes for a variety of problems of a product will be grouped into an update. If a vendor updates a software product on a regular basis, the download size of the update package will continue to grow, because the vendor cannot omit files under the assumption that the user already has those files from earlier updates. Because the update package combines a number of whole files, it may be quite large, even when the files are compressed. Sometimes, even on the fastest modem connections, the bandwidth efficiency of the download is decreased.
The time-consuming aspect of the conventional downloading process is, of course, undesirable. In some cases, customers pay long-distance or connection time charges during these file downloads. Any reductions in connection time will reduce the direct monetary cost for these customers. The vendors typically also have some distinguishable costs relating to the sizes of downloads they provide, so reducing the sizes may give them direct monetary benefits as well. Reducing the sizes of downloads will increase their available network bandwidth, allowing them to serve more customers with existing network server equipment.
The long time it takes to download a large update also makes the downloading process more vulnerable to various network connection problems. There are a number of reasons why an Internet session might be disconnected prematurely, including telephone line noise, call-waiting signals, and unintentional commands. Some Internet service providers enforce a connection time limit, limiting the amount of time the user can be on-line in a single session. If the user is downloading a large file when the network connection is cut off, he or she may have to start over. Most common operating systems and file transfer protocols do not allow the file transfer to be resumed, so any interim progress would be lost, and the transfer would have to be restarted. The opportunities for failure are so numerous that many users find it nearly impossible to obtain the update online. If the size of an update package is too large, users may never be able to completely download it.
One attempt to reduce the size of software updates and increase bandwidth efficiency relates to the use of delta patches, or binary patches. One skilled in the relevant art will appreciate that a delta patch corresponds to specialized software code that modifies an existing file when executed by a computing device. Because the delta patch includes specialized software code, a unique delta patch is required for each unique version of a file. As applied to software updates, a software update service can transmit a smaller sized update delta patch instead of transmitting a complete, updated file. The updated delta patch is then utilized to modify the existing file into the updated file.
Although the update delta patches can potentially reduce the amount of data required to update files, current approaches to delta patching are deficient in managing the selection of applicable delta files in situations where a large number of versions of a file exist. Because a unique delta patch is required for each version of a file, typical software update systems can often require hundreds, if not thousands, of unique delta patches to correspond to each unique version of a file. In one approach, some update services supporting delta patching transmit all possible delta patches to a client computing device. However, this approach typically increases the amount of data required to implement the software update as the number of possible update delta patches increase. Accordingly, the number of potentially applicable delta patches can quickly grow to the same size as the complete updated file. In another approach, a networked update software service scans a client machine to select which delta patch may be applicable for each client machine. Although this reduces the amount of delta patch information that is transmitted, it requires additional logic on the software update service to scan the client machines and select an applicable delta patch. The use of the additional logic increases the system resources that must be provided by the service. Further, this approach typically prevents the utilization of network caching, such as is typically achieved by traditional Web servers.
In addition to the above described shortcomings, existing systems are unable to deliver certain types of software updates, such as hardware drivers. As known in the art, specialized software updates, such as those that apply to hardware drivers, are difficult to provide to users on a large-scale distribution because most specialized software updates will only work on client computers with specific hardware. In most cases, for example, if a client computer obtains an incompatible hardware driver upgrade, the installation of the driver upgrade may cause a fatal error, or even prevent the computer from operating.
As will be readily understood from the foregoing, there is a need for a system and method having improved communication of software updates between a server and a number of clients. In addition, there exists a need for a software update system and method having improved mechanisms for allowing update services to target specific types of clients when delivering specialized updates.